The metallic cap having the so-called “pilfer-proof (or tamper-evidence) function” is employed widely and generally in various beverage containers or the like in the prior art. In this pilfer-proof function, the weakening portion of the pilfer-proof band formed at the bottom of the skirt portion of the cap is ruptured, when the cap is removed (by turning it counter-clockwise, for example) for the first time to open the container, so that the opening of the container may be clearly indicated to prevent a tampering use. The cap of this kind is divided into a plurality of types according to the difference in the structure for rupturing the pilfer-proof band. In one type of such metallic pilfer-proof cap (as abbreviated into the “PP cap”), a plurality of slits formed at a predetermined circumferential interval in the skirt portion and a plurality of bridges positioned between the slits are not ruptured when the cap is turned and removed.
There is also known a type (or Type 1), in which a plurality of vertical scores are formed at a predetermined interval in the bottom of the skirt portion and extended perpendicularly of the horizontal slits. The vertical scores formed to reach the slits from the positions spaced at a predetermined distance from the lower end of the skirt portion. The vertical scores are ruptured by turning the cap screwed on the container mouth.
In another known type (or Type 2), there are formed wider bridges, in which vertical scores are directed in the directions perpendicular to the horizontal slits, and other bridges which can be ruptured more easily than those wider bridges. When this cap of Type 2 is turned and removed from the container mouth, the bridges other than the wider bridges are ruptured at first, and the vertical scores formed in the wider bridges are then ruptured. As a result, the pilfer-proof band is cut into an open state so that it is removed together with the cap from the container mouth. Here, one vertical score is formed from the position at a predetermined spacing from the lower end of the skirt portion to the slit circumferential portion.
There is further known a cap of the type (or Type 3), in which all the narrower bridges are broken, when the cap is turned and removed, so that the pilfer-proof band cut off the cap is left in the ring shape on the side of the container mouth.
The first one of the aforementioned three types is disclosed not only in the specification of U.S. Pat. No. 3,771,683 but also in the specifications of U.S. Pat. Nos. 3,812,991, 3,861,551 and 4,217,989.
The pilfer-proof cap of the aforementioned first type is moved upward as it is turned counter-clockwise. However, the upward movement of the pilfer-proof band is blocked by the annular bulging portion of the container mouth. Therefore, the vertical scores formed in the skirt portion are ruptured to widen the bottom of the skirt portion, and this widened skirt portion can ride over the annular bulging portion so that the cap can be removed from the container mouth.
Therefore, the pilfer-proof cap of this type is advantageous in that it can be judged in view of the appearance of the ruptured and widened vertical scores of the skirt portion whether or not the cap has been once opened.
In the cap of this type, however, the vertical scores formed in the skirt portion are ruptured to expose their shape ruptured faces to the outside, and may injure the hand or the like of a consumer.
Moreover, the bottom of the skirt portion is ruptured and widened along the vertical scores so that the appearance gives a poor looking. The skirt portion ruptured along the vertical scores is an obstacle, and the consumer may separate the skirt portion from the cap body and may throw it to the places other than the garbage pit. This raises a problem of scattering the garbage. Even if the bottom of the skirt portion is removed from the cap body, the residues of the bridges may be left on the end portion of the cap skirt to injure the hand or the like of the consumer.
Thus, a second type has been conceived and disclosed in the specification of U.S. Pat. No. 4,205,755.
In the pilfer-proof cap of this second type, the cap is moved upward by turning the cap counter-clockwise, but the pilfer-proof band is retained and prevented from upward movement by the annular bulging portion of the container mouth. Consequently, ruptures occur at bridges other than one wide bridge and then at the vertical scores in the wide bridge so that the pilfer-proof band is ruptured. As a result, the pilfer-proof band can be removed together with the cap from the container mouth.
Therefore, the pilfer-proof cap of this type is advantageous in that its once opening can be judged from the appearance even if it is closed again, because all the bridges other than the wide bridge are ruptured together with the vertical scores when the cap is once opened.
However, the pilfer-proof band still attached in the ruptured state to the cap raises an obstacle, and the pilfer-proof band in the ruptured state may be cut off the body portion of the cap and discarded to a place other than the garbage pit. This discard raises a cause for scattering the garbage. Moreover, the fingers or the like may be injured when the pilfer-proof band is torn off the body portion of the cap.
A cap of a third type is disclosed in Japanese Utility Model Laid-Open No. 61-175144. In the pilfer-proof cap of this type 3, the cap is moved upward by turning it counter-clockwise, but the upward movement of the pilfer-proof band is blocked by the annular bulging portion of the container mouth. Therefore, all the narrow bridges of the pilfer-proof band are ruptured so that the pilfer-proof band cut off the cap is left in the ring shape on the container mouth.
According to the cap of this type 3, therefore, the problem of scattering the garbage or the like can be solved. Therefore, the cap of the type 3 is superior because it can solve the problems intrinsic to the caps of the remaining two types.
Here, the metallic pilfer-proof cap having the pilfer-proof band at the bottom of the skirt portion is mounted, no matter what type it might belong to, on the container mouth by employing the well-known metallic cap rolling apparatus. Specifically, the cap is rolled on, while being loaded (as a top load) on its top end wall, by the individual shaping rolls of that apparatus, so that the cylindrical portion of the skirt portion is deformed and internally threaded according to the external thread of the container mouth. At the same time, the lower end portion of the pilfer-proof band, which is formed at the bottom of the skirt portion, is rolled to engage with the lower end portion of the annular bulging portion of the container mouth.
On the other hand, the description is made on the container mouth to be crowned with the cap of the third type. This container mouth is usually provided, below the externally threaded area, with the annular bulging portion for retaining the pilfer-proof band and, below this annular bulging portion, with the diametrically smaller cylindrical portion having a diameter substantially equal to that of the root of the external thread. This container mouth of the most popular shape is crowned with the cap, as described above. When the cap is to be removed for the first time from the container mouth to open the container by turning it counter-clockwise, the cap itself is moved upward, but the pilfer-proof band is prevented from moving upward by the annular bulging portion of the container mouth. As a result, the weakening portion of the pilfer-proof band is ruptured so that the pilfer-proof band is separated from the cap.
Here in the metallic pilfer-proof cap of the prior art, as disclosed in Japanese Utility Model Laid-Open No. 61-175144, the horizontal slits are formed along the circumferential direction of the cap in a manner to leave the bridges so that the bottom of the skirt portion may be the pilfer-proof band. In this case, the horizontal slits are formed by a slit punch tool, which is provided with shearing blades at a predetermined narrow interval on the outer edge in the circumferential direction, excepting the bridge portions. Specifically, as shown in FIG. 13, by employing a slit punch tool 34B providing an upper face side with a shearing plane normal to the cap wall and a lower face with a slope face, horizontal slits 16 are formed to offset (or displace) the lower side of a shearing plane X radially more inward of the cap than the upper side, as shown in FIG. 12B. Moreover, the portions having no shearing blade of the slit punch tool 34B leave the portions connected by bridges 17B, as shown in FIG. 12A. (Here, the concept of vertical directions accords to the vertical directions of the cap.)
Here is examined the metallic pilfer-proof cap of the prior art type, in which the pilfer-proof band is left on the side of the container mouth when the cap is opened. In this case, a container mouth 2 is crowned with a cap 1, as shown in FIG. 14A and FIG. 14B, from the unused state shown in FIG. 11, by the rolling-on operation. When the cap 1 is then removed for the first time from the container mouth 2 to open the container by turning the cap 1 counter-clockwise, the pilfer-proof band 15 left at the container mouth 2 is caught at its upper end by the container mouth 2, because the pilfer-proof band 15 is offset near its upper end inward at the time of forming the horizontal slits so that it is pushed onto the side of the container mouth 2. As a result, the pilfer-proof band 15 does not slip down naturally but is fixed at its mounted position. When, however, the container mouth 2 is re-sealed with the cap 1 once removed, the cap 1 merges into the pilfer-proof band 15 left on the container mouth 2, as shown in FIG. 15B. At a glance, therefore, it is not easily found that the container has already been opened. This may fail to provide the pilfer-proof effect sufficiently.
Moreover, the bridges 17B formed between the horizontal slits 16 are located on the lower side of the shearing plane of the horizontal slits 16. When the bridges 17B are ruptured to cut the pilfer-proof band 15 off the cap 1, the residues (i.e., relatively large ruptured pieces) of the bridges 17B are left on the side of the pilfer-proof band 15, which is left in a ring shape on the container mouth 2. As a result, the lips or the like of the consumer may be injured by the residues of the bridges 17B left on the side of the pilfer-proof band 15, when the consumer drinks the beverage with his or her mouth directly from the container mouth 2.
The present invention has an object to solve the problems thus far described. The specific object of the invention is to provide a metallic pilfer-proof cap of the type, in which a pilfer-proof band is left in a ring shape on the side of a container mouth. According to the invention, the pilfer-proof band once cut off the cap is not placed in the original cap-mounted state on the side of the container mouth thereby to provide the pilfer-proof effect sufficiently. Moreover, the safety at the using time can be retained by clearing the side of the pilfer-proof band cut off the cap, of the residues of the bridges.